To go by the statements of most mainstream economists, one would be forgiven for believing this is the best of times for Keynesian economics.

Fans of John Maynard Keynes, the renowned early 20th-century economist who developed the theory on how nations could dig themselves out of an economic downturn, have been running victory laps since the collapse last month of the claim by the Harvard economists Carmen M. Reinhart and Kenneth S. Rogoff that economies tend to slow significantly after government debt reaches 90 percent of gross domestic product.

Then, as if on cue, the number-crunchers in Brussels announced last week that the economy of the euro area countries — which have been following a decidedly non-Keynesian path — shrank yet again at the beginning of the year. It was the region’s sixth quarterly contraction in a row.

The confluence of events provided further evidence of Keynes’s central proposition: when consumers and businesses set out to reduce their debt burden, and private spending and investment stall, it is the government’s job to borrow, spend and pick up the slack.

The claim by Ms. Reinhart and Mr. Rogoff had provided an intellectual foundation to the demand by House Republicans, British Tories and Germans that indebted governments should move quickly to reduce their budget deficits and the burden of debt.

Its demise — at the hands of a graduate student from the University of Massachusetts, Amherst, who discovered flaws in the Harvard economists’ methods — left a more modest assertion in its wake: heavily indebted nations grow more slowly. Yet it is not even clear that debt necessarily depresses growth. The track record from Europe and elsewhere suggests that austerity programs that hold back growth often make the debt burden even worse.

Two economists — Lawrence H. Summers of Harvard, President Obama’s former chief economic adviser; and Brad DeLong of the University of California, Berkeley — proposed in a recent paper that at the rock-bottom interest rates that prevail today, government spending to encourage growth would in fact pay for itself. In the United States, they concluded, it would lighten the nation’s future debt burden — not increase it.

But in many ways it is the worst of times for Keynesian economists. For despite all this intellectual firepower, governments across the industrial world are zealously tightening their belts.

The Italian government has cut its annual budget deficit to 3 percent of G.D.P. last year from 5.5 percent in 2009, and the Irish government has slashed it to 7.6 percent from 13.9 percent. In Britain — which has its own currency and is freer than its euro-area neighbors to set policy — the government of Prime Minister David Cameron reduced the deficit to 6.3 percent of G.D.P. last year, down from 11.5 percent in 2009.

“We will not be able to build a sustainable recovery with long-term growth,” Mr. Cameron said in a speech in March, “unless we fix this fundamental problem of excessive government spending and borrowing that undermines our whole economy.”

The German government is running a budget surplus. And despite the public’s belief that Washington is engaged in a spending spree, the deficit in the United States narrowed to 7 percent of G.D.P. in 2012 from 10.1 percent in 2009.

None of these countries are growing much, mind you. In the United States, unemployment is still stuck at 7.5 percent. In its latest economic forecast last month, the International Monetary Fund predicted that the nation’s economy would grow only 1.9 percent this year, slowed by further budget-cutting.

What explains the gap between theoretical victory and policy defeat? Voters appear to want everything — including more jobs and a smaller deficit. Is resistance to fiscal stimulus simply a matter of political tactics? Do Republicans automatically oppose anything coming from a Democratic administration they loathe?

Photo

In Greece, street vendors gave out free produce last week during a 24-hour strike against government plans to open up the sector.Credit
Louisa Gouliamaki/Agence France-Presse — Getty Images

Economists have articulated other tempting possibilities. One is that moral views are getting in the way of reason: the decisions of both elected officials and voters are driven not by economic research but by a belief in the virtue of thrift drawn from The Ant and the Grasshopper.

Another is that policy serves the interests of moneyed creditors, lenders who fear that heavily indebted governments will be tempted to default, permit higher inflation to erode the debt’s real value or tax the wealthy more heavily in the future.

N. Gregory Mankiw of Harvard, a former chief economic adviser to President George W. Bush, has proposed another reason, rooted in a notion of democratic rule.

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“If the goal of government is to express the collective will of the citizenry, shouldn’t it follow the lead of those it represents by tightening its own belt?” he wrote in a recent paper. “If we as individual citizens are feeling poorer and cutting back on our spending, why should our elected representatives in effect reverse these private decisions by increasing spending and going into debt on our behalf?”

These propositions probably hold some truth. Yet they rely on a misdiagnosis of our economic circumstances. The world’s recent experience suggests fairly strongly that excessive thrift will make us all poorer. If everybody stops consuming and starts saving at the same time, there will be a lot fewer jobs producing stuff to consume.

There are two additional arguments that rely less on a misreading of economics. The first, which applies primarily to the euro area, has to do with the distribution of the costs of fiscal stimulus and austerity.

The idea that austerity is the solution for the economic crisis in Greece, Spain, Italy and other weak economies of the euro area is appealing in Germany precisely because it demands sacrifices of the citizens of the periphery. Keynesian stimulus would require German money.

The other argument derives from a seemingly myopic conflation of the short and the long term: worried about the scary rise of Social Security and Medicare spending in future decades, voters demand budget cuts now.

This self-defeating demand is the main driver of economic policy in the United States today.

Yet the voters’ position is not irrational. Americans’ unwillingness to support more spending now comes from an entirely reasonable mistrust of the government’s willingness to cut spending later.

Fortunately, there is a way to square the circle, if only our political masters could overcome their partisan animus to embrace it. The answer is to combine some stimulus in the present — via tax cuts or more public spending — with transparent, legally binding initiatives to limit spending in the future.

For instance, the administration could propose raising the retirement age a decade down the road. It could also save a lot of money by rejiggering Medicare’s cost-sharing formulas. The higher-income elderly could be made to shoulder a larger share of their health care costs in the future.

Swapping future cuts in Social Security and Medicare for more spending today will not be an easy deal. Liberal Democrats will balk at trimming the social safety net. House Republicans appear immune to any fiscal compromise.

The Obama administration has tried some of this at the margin. It proposed changing the price index used to adjust Social Security benefits, slowing their rise. It has had no success.

But a deal along these lines offers a plausible political path toward an economic policy that is not quite as self-destructive as the one we’ve got. The goal: Keynesian today, when the economy needs it, but not tomorrow.

A version of this economic analysis appears in print on May 22, 2013, on Page B1 of the New York edition with the headline: A Keynesian Victory, But Austerity Stands Firm. Order Reprints|Today's Paper|Subscribe